Silent gear



R. W. LYTLE SILENT GEAR Original Filed Oct. 1930 Dec. 20,- 1932.

wheels of the silent gear type.

are commonly made from a laminated prod-- Patented Dec. 20, 1932 UNITEDSTATES ROBERT W. LYTLE, OF CINCINNATI, OHIO, ASSIGNOR TO THE FORMICAINSULATION PATENT orr cr.

COMPANY, or CINCINNATI, OHIO, A CORPORATION or oHIo SILENT GEAR This.invention relates particularly to gear Such gears uct composed of clothor canvas impregnated with a varnish ofbakelite, redmanol, or the like,the mass-being compacted and hardened under heat and pressure. Such agear is expensive; and where the gear is formed by cutting blanks from alarge, thick sheet of the laminated. product referred to, one cannoteconomize in the use of materials.

Among laminated products of the charac: 'ter m'entionedabove which havebeen known on the market for years, may be mentioned formica andmicarta.

Molded gear-blanks have'heretofore been produced. One method which hasenabled such agear blankto be produced at moderate cost is a method inwhich an annulus comprising layers .of cloth impregnated with a binderhas been built up, and a web. has been provided within the annulus,composed of abinder and macerated'cloth, for example.

Such a gear isunsatisfactory in some respects and does not. possess asgood strength as de- The primary object of the present invention istoprovidean improved silent gear and an improved method of making thesame; In

the improved gear, use is made of a ring or annulus comprising layers ofcloth impregnated with bakelite varnish, for example, a

center-structure comprising layers of cloth impregnated with bakelitevarnish, with spaces intervening between the center-structure and theannulus; and moldlng compound in the spaces between, thecenter-structure and the rim or annulus. A structure, or assembly,

rials.

of this character may be consolidated and hardened under heat andpressureein' a suitablemold,'- and thus one may produce a gear blankhaving the requisite strength and effect a'veryinaterial economy in the'useof, mate- In the molding operation, the heat converts the bakelitetoan infu'sible and substantially insoluble condition.

a The invention is illustrated 'in' a preferred embodiment in theaccompanying drawing, in whichat 1 1 Fig. 1 is aplan view of the.improved gear;

this application filed m 6 .Fig. 2, a section taken as indicated atline2 of Fig. 1; Fig. 3, aplan view (partly bro-ken) illustrating themanner in which-the gear-1s built up; Fig. 4,: an enlarged broken viewwhich is sectional and somewhat diagrammatic in character; Fig. 5, abroke'nplan view illustratingthe manner in which the'poly onal sheets ofthe center-structure preferably are formed; and Fig. 6, a similar viewillustrating a modification.

In the preferred practice, the

assembly from which the gear-blankis molded is built up asf'ollows: Anannulus A and a-centerstructure B are built up from pliesof duck.nnpregnated with a potentially reactive phenolic condensation productvarnish, such as bakelite, the shape of the plies of the cen-.

tially; reactive bakelite resin. The structure is introduced into amoldand molded under heavy pressure ata hightem'peratur'e until the binderis transformed to an .in-

fusible and substantially insoluble condition, The manner in whichthis-maybe effected is now well understood in the art.

The fabric employed maybe any suitable fabric, suchas duck,v canvas,paper or the like. duck is employed.

An important feature there is a waste of in the neighborhood of" 17%.Inasmuch as materialof this characfor 1s. necessanly rather expenslvethe cost of of the inventionfis' that whichenables the-plies of materialwhich Preferablv, however, a good-grade of gears produced fromimpregnated cloth cut: into d1sks,;or from previously manufactured"impregnated heavy sheets, is. excessive.

nulus A may be formed in. any desired manner. Preferably, however, it 1sbullt up of v According to the present invention, the an- I I are used.

exteneing between the plies which form the annulus A. These squarespreferably are supplemented by small impregnated fabric disks 4- whichmay he placed between or upon the squares and which serve to form athickened hub-portion, as indicated at 5.

tion, holes 6 may be punched in'the plies Which form thecenter-structure, thus pro- Fig. 6 illustrates the manner in whichtriangular plies 3 may be punched from a strip without substantialwaste. The triangular plies may be substituted for the square plies, ifdesired. Preferably, however, the squares It appears from what has beenstated that polygonal fabricplies having four sides or less may beemployed and these may be punched from a stri or sheet without anyconsiderable waste 0 material.

The molding compound-employed for filling the spaces 1 may be anysuitable molding compound. Preferably a molding compound composed ofwood flour and a potentially reactive phenolic condensation product isemployed; and preferably the potentially reactive binder of the moldingcompound is sufliciently far reacted before it is introduced to enableit to harden slightly in advance of the hardening of the binder in thefabric plies forming the rim-structure and center-structure. 1 Themolding compound may be, for convenience, preliminarily compacted intosmall balls which may be readily introduced into the cavities, theseballs of molding compound being of suitable size and number to affordthe requisite amount of material 1n the cavities.

Preferably one or more complete disks 7 of impregnated fabric areemployed at one side of the assembly from which the gear-blank ismolded. This gives a certain continuity to the web-structure andrim-structure, the disk rim-portion as well as the center-structure ofthe assembly.

In the molding operation, the molding compound is' more plastic and morefree to flow than are the impregnated plies of duck employed in therim-structure and center-strucplication is a division. 'or disks 7serving as a foundation for the formed and there is no danger of Warpingcenter perforations 6 of the plies of the centerstructure and thus abore adapted to receive a shaft will. be formed in the finishedgearblank. i

It is preferred, as indicated above, to have the molding compound ofsuch nature that it wi l harden slightly in advance of the re mainder ofthe structure, the purpose being to v bridge thespaces between the edgesof the Fig. 5 illustrates the manner in which squares 3 may be punchedfrom a strip of impregnated fabric. In the punching operabeing providedwith teeth. Ordinarily, teeth are provided for positive transmlssion,gears of this character being used largely in automobiles at the presenttime; I It will benotedthat the web-portion o the gear, that is, theportion within the rimpor'tion, consists of a combination of two typesof material which may be molded and compacted, namely, thecenter-structure which comprises the impregnated fabric and themoldingpowder which is used to fill the spaces between thecenter-structure and the-- rim. Thus, the two different materialsencircled by the rim-portion are possessed of different elasticity orresilience characteristics, tending to produce inequal frequencies ofvibration and thereby neutralize high tone vibrations. This resultsin-improvlng the silent quality ofthe gear in operation. The

fabrics employed give the necessary strength; and the shapes andrelation of the plies of fabric enable a gear of economical crosssectionto be produced. I The molding compound in the spaces between thecenter-structure and the rim-structure may perha s have somewhat of acushioning effect.- hiefly,

'however,the improved silent quality of the gear is attributed by me tothe differences in texture 'or composition which exist'between thefabric portions and the bodies formed from the molding compound C.

The improved gear claimed herein may be manufactured advantageously bymeans of the process described and claimed in my pendingapplication'Serial No. 488,123, filed present ap- 12 October 28, 1930,of Which-the What I regard as new, and desire to secure by LettersPatent, is: 1. A gear asspecified in claim 5, in whic "thecenter-structure comprises polygonal sheets, each having not more thanfour edges.

3.;A gear comprising-a circular disk of fabric impregnated witharbinder, an annu-,

lus comprising layers of fabric superposed on the marginal portion ofsaid disk, a centerstructure comprising layers of fabric im-- pregnatedwith a binder and of polygonal form, with spaces between saidcenter-structure and said annulus, and molding com pound in said spaces,the whole consolidated under heat and pressure.

4. A gear as specified in claim 3, in which the polygonal layers of thecenter-structure have not more than four edges.

5. A gear comprising a compacted, hardened structure and comprising anannulus composed of layers of fabricand a binder, a center-structurecomprising layers of polygonal sheets of fabric and a binder, withspaces between the annulus and the center-structure, and a mouldingcompound in said spaces,.the whole consolidated under heat and pressure.

ROBERT W. LYTLE.

